MAP41: O of Destruction! (PlayStation Doom)

MAP41: O of Destruction! is the forty-first level of the Sony PlayStation and Sega Saturn versions of Doom, and the eleventh level of the Doom II episode. It is based on the original MAP11: 'O' of Destruction! (also known as Circle of Death), with modifications made to adapt the map to the consoles' limitations. The author of the original map is John Romero.

Essentials
Proceed along the walkway to your right and take a right across the bridge into a dark metal area. Climb the stairs to another outdoor area with trees, then proceed up either staircase into the structure ahead of you. Once you pass through the doorway inside the structure, an arachnotron will be released to defend the blue keycard in the room. Take cover behind either side of the door if needed. Once the arachnotron is dead, re-enter the room and pick up the blue keycard. Now return to the main area of the level.

Make your way along the walkway to the opposite (west) side of the area and go through the blue door. Follow the path to a room with a gargoyle switch in the center and press it. Continue through this room, up the small staircase, and along a ledge which is rising. Press the switch on the other side of the ledge and return to the main area once again. Continue along the walkway to its north side, and cross the newly created bridge to the red keycard on the central platform.

Drop down into the sludge to the north-west of the central circular walkway and head through the red door. Proceed through the hallway, towards the metal bars (which will automatically open), and up the stairs, arriving at a pillar with another gargoyle switch. Press it to lower a barrier on the walkway just outside. From here, drop into the sludge and follow the walkway round to the right until you find a gargoyle switch in a green pillar. Press this to lower the nearby floor which will put you back on the circular walkway. Go round to the north side and run across to the platform you opened earlier. Follow the platform until you drop into a dark cave. Dispose of the enemies here and head through the brightly lit tunnel in the green structure ahead. You should now be in an "E"-shaped sludge room. Ride the lift in the upper prong of the "E" up to a switch. Press it, ride the lift back down, and run into the timed lift that just lowered in the lower prong of the "E". Press the switch there to open the gate to the exit switch.

Other points of interest
As the level starts, there is a staircase on the other side of the wall behind you. This staircase allows you to get out of the sludge if you fall into it, and also has a shotgun at the bottom.

Before climbing the metal staircase in the room east of the O, turn round and look at the walls either side of the entrance. You will see a pool of blood in front of the wall on your left; you can walk through this wall to find a soulsphere behind it.

A plasma gun can be found in the blue keycard room, behind the box that held the arachnotron.

When you press the switch that lowers the barrier blocking the northern walkway, the pillar it is attached to will lower to reveal a rocket launcher.

When you drop into the dark room before the exit, hug the wall on your right and follow it round to find a BFG9000 hidden behind the green structure.

At the very end of the level, just before the exit switch, you will see a teleporter to your right. Step into it to reach a high ledge overlooking the O which holds another soulsphere. After getting the item, walk back along the ledge to drop back into the dark room leading to the exit.

Secrets

 * 1) When you reach the top of the metal staircase in the room east of the O, a lift will lower in the wall south of the staircase. Ride this lift up to a small room with a chaingun. From here, open the wall with pipes next to the chaingun to find a passage leading outside. (sector 117) When you reach the end of the passage, drop down to find a platform with a partial invisibility.
 * 2) After retrieving the blue keycard, return to the O. Along the eastern wall in the northern half of the nukage lake, a small doorway will have opened. Go through (sector 159) to a room with five boxes of rockets and take the teleporter at the end to reach the imp's ledge inside the O, which also holds two energy cell packs.
 * 3) After passing through the red door, you will go through a set of metal bars that automatically open. The wall alongside the northern-most bar can be opened when the bars are open. (sector 10) Take the passage out to the sludge pit beyond the barred window, where you will find an invulnerability powerup.

Bugs
Because of a peculiarity of the Doom engine that allows players to press a switch no matter how far above or below it they are, one can skip a large amount of the level by pressing the gargoyle switch at the top of the staircase past the red door while standing in the sludge below it. They can then jump onto the cement walkway leading to the exit area from the circular walkway.

Comparison of versions
Numerous changes were made to this level compared to the PC version.

Room design

 * Several staircases have fewer steps.
 * All nukage and water flats are changed to sludge.
 * All switches use a gargoyle face on metal wall texture (named on PC), except for the exit switch which continues to use a knife switch on computerized skull texture (though on console ports, the exit switch starts in the off position, ).
 * A number of hidden sectors are added around the outer walls of the O, and inside the pillars supporting the O. These allow the sludge pit sectors around the O to be taller than 256 units without distorting the wall textures.
 * The heights of the outdoor area around the blue and the north-eastern room leading to the exit are reduced.
 * A bloody meat hook decoration is added to the room containing the blue keycard.
 * The textures of the blue keycard plinth scroll right instead of left.
 * The number of bars blocking the corridor behind the red door is reduced from seven to five.
 * The north walkway leading to the exit area is closer to the O, probably to assist with making the jump using console controls.
 * Hidden sectors are added to the lifts in the stone structure before the exit, to avoid any texture distortions as the lifts lower and rise.
 * The walls either side of the exit switch are diagonal rather than straight.

Monster placement

 * Lost souls are replaced with shotgun guys.
 * Pain elementals are replaced with cacodemons.
 * Hell knights are replaced with chaingunners.
 * Zombiemen are either replaced with shotgun guys or removed entirely.
 * The arch-vile guarding the blue keycard is replaced with an arachnotron.
 * The revenant at the top of the staircase past the red door is replaced with a cacodemon.
 * A spectre behind the red door on Hurt Me Plenty and Ultra Violence skill levels is replaced with a nightmare spectre.
 * The cyberdemon found in the center of the O in multiplayer is absent.

Other differences

 * In v1.9 of Doom II, lowering the column with the rocket launcher next to the revenant also lowers a nearby platform, allowing you to leap straight to the ledge on the north side of the O. This platform is missing from console ports because they are based on v1.666.

Music
The map uses the following music tracks:

Player spawns
This level contains seven spawn points:
 * 1) facing north. (thing 122)
 * 2) facing south-east. (thing 123)
 * 3) facing east. (thing 124)
 * 4) facing east. (thing 125)
 * 5) facing west. (thing 126)
 * 6) facing south-west. (thing 127)
 * 7) facing west. (thing 128)

Things
This level contains the following numbers of things per skill level: